scholarly journals The Effeots of the Dipyridyl Diquat on the Metabolism of Chlorella Vulgaris I. Gas Exchange in the Light

1970 ◽  
Vol 23 (1) ◽  
pp. 43 ◽  
Author(s):  
JS Turner ◽  
DM Stokes ◽  
Lynnor B Gilmore
Keyword(s):  
Gas Exchange ◽  
Oxygen Uptake ◽  
Chlorella Vulgaris ◽  
Maximum Rate ◽  
Toxic Substance ◽  
Irreversible Inhibition ◽  
Green Tissue ◽  
Rapid Fall ◽  
Dark Metabolism ◽  
Respiratory Apparatus

The effects of diquat on gas exchange in illuminated C. vUlgaris have been studied by manometric procedures. Estimates of dark oxygen uptake were made by transfer of treated cells to darkness. Analysis of the results indicates that on adding diquat to C. vUlgariB there is a rapid fall in the rate of apparent photosynthesis. This is due to an immediate and large increase in dark metabolism (C02 and O2 exchange) accompanied by irreversible inhibition of real photosynthesis firstly, then of respiration. At some unspecified stage a light-dependent oxygen uptake begins, rises to a maximum rate, and declines to a low value, continuing after the inhibition of respiration. These results are discussed in relation to the known effects of diquat on plastid reactions and to the hypothesis that in illuminated green tissue diquat produces a toxic substance which damages both the photosynthetic and respiratory apparatus.

Mass Spectrometry Analysis of Oxygen Gas Exchange in High- and LOW-CO2 Cells of Chlorella vulgaris

1988 ◽  
Vol 43 (9-10) ◽  
pp. 709-716 ◽  
Author(s):  
Y. Shiraiwa ◽  
K. P. Bader ◽  
G. H. Schmid
Keyword(s):  
Gas Exchange ◽  
Oxygen Uptake ◽  
Chlorella Vulgaris ◽  
Mitochondrial Respiration ◽  
Mass Spectrometry Analysis ◽  
Strong Light ◽  
Inlet System ◽  
Light Intensities ◽  
Oxygen Gas ◽  
A Minor

Abstract Oxygen gas exchange was monitored in the unicellular green alga Chlorella vulgaris 211 - 11 h by means of a mass spectrometer equipped with a special membrane gas-inlet-system and a photosynthetic reaction vessel. CO2-dependent 18O2-uptake as well as 16O2-evolution were analyzed in both High- and Low-CO2 cells. In High-CO2 cells, the 18O2-ruptake in the light (UL) decreased by 65% upon addition of 3 mᴍ NaHCO3 , while 16O2-evolution (E) was increased approx. 1.8 times by the same treatment. 18O2-uptake in the dark (UD) was not affected by the addition of external inorganic carbon (Ci). The addition of 3.3 mᴍ NaHCO3 also affected UL and E in Low CO2-cells, however, to a minor extent. UL under CO2-saturating conditions was light intensity-independent up to 2 klux and 1.2 klux in High- and Low-CO2 cells, respectively. Above these light intensities UL increased approx. 4-fold in High- and approx. 6-fold in Low-CO2 cells. Under CO2-limiting conditions, however, UL increased in High-CO2 cells even under very low light intensities, showing that photorespiratory oxygen uptake occurred even in the near vicinity of the light compensation point. Under C02-saturating and strong light conditions UL represented almost half of E in Low-CO2 cells and about 30 % of E in High-CO2 cells. In Low-CO2 cells addition of ethoxyzolamide (EZA), an inhibitor of carbonic anhydrase, enhanced UL and suppressed E and NET under CO2-limiting conditions, whereas the compound had only a minor effect on High-CO2 cells. DCMU (3 μᴍ) strongly inhibited E and UL under CO2-saturating conditions, with the remaining UL being smaller than UD . KCN (1 mᴍ) and SHAM (1.5 mᴍ) added to DCMU-treated Low-CO2 cells suppressed UL by approx. 50 % . The resulting value corresponded to half of UD . KCN also inhibited E under CO2-saturating conditions, with UL being strongly enhanced showing a maximal uptake at 0.4 mᴍ KCN . Under these conditions NET was nearly zero. The effect seems to be due to an inhibition of RubisCO and an enhancement of Mehler reactions. At 0.7 mᴍ KCN , DCMU entirely inhibited UL , but oxygen uptake appeared increased after turning the light off. This uptake corresponded to approx. 60 % of UD . Whereas KCN and SHAM inhibited approx. 70 % of UD , only 16% of UL was suppressed. These results suggest that the contribution of mitochondrial respiration to UL was negligeable, since UL seemed to be suppressed in the light under CO2-saturated conditions. Iodoacetamide, which is an inhibitor of the Calvin cycle and thereby diverts carbon into the respiratory pathway, inhibited E and NET under CO2-saturating conditions, but did not affect UL . This result also shows that UL is not due to mitochondrial respiration. A hydroxylamine derivative [20, 21] which changes the ratio of the RuBP carboxylation to oxygenation activity in tobacco leaves did not affect this ratio in Chlorella.

scholarly journals The Effects of the Dipyridyl Diquat on the Metabolism of Chlorella Vulgaris III. Dark Metabolism: Effects on Respiration Rate and the Path of Carbon

1971 ◽  
Vol 24 (3) ◽  
pp. 433 ◽  
Author(s):  
DM Stokes ◽  
JS Turner
Keyword(s):  
Citric Acid ◽  
Oxygen Uptake ◽  
Carbohydrate Metabolism ◽  
Chlorella Vulgaris ◽  
Dark Respiration ◽  
Complete Darkness ◽  
Tracer Studies ◽  
Rapid Accumulation ◽  
Dark Metabolism ◽  
Stimulation Of

When O. vulgaris is treated in complete darkness with diquat at concentrations which are toxic in the light, there is a rapid and large stimulation of oxygen uptake with no significant alteration in the R,Q. If the O. vulgaris has been darkened for some hours before the addition of diquat there is a two- to threefold stimulation of the rate of respiration, which subsequently remains constant or falls only slowly for up to 500 min. With pre-illuminated or glucose-treated O. vulgaris, diquat causes a much greater stimulation of dark respiration, rapidly declining to near the control rate. Tracer studies with 14C02 and [14C]glucose show that diquat when added in darkness to O. vulgaris accelerates the breakdown of starch and the loss of 14C from most intermediate substances of carbohydrate metabolism. The exception to this is the rapid accumulation of 14C counts in citric acid. These results are discussed and a mechanism for the action of diquat in darkness is proposed.

Pulmonary Gas Exchange and Oxygen Uptake During Exercise in Patients with Type 1 Diabetes Mellitus

1992 ◽  
Vol 9 (3) ◽  
pp. 252-257 ◽  
Author(s):  
Th. Wanke ◽  
D. Formanek ◽  
M. Auinger ◽  
H. Zwick ◽  
K. Irsigler
Keyword(s):  
Diabetes Mellitus ◽  
Type 1 Diabetes ◽  
Gas Exchange ◽  
Oxygen Uptake ◽  
Type 1 Diabetes Mellitus ◽  
Pulmonary Gas Exchange

scholarly journals Coca chewing for exercise: hormonal and metabolic responses of nonhabitual chewers

1996 ◽  
Vol 81 (5) ◽  
pp. 1901-1907 ◽  
Author(s):  
Roland Favier ◽  
Esperanza Caceres ◽  
Laurent Guillon ◽  
Brigitte Sempore ◽  
Michel Sauvain ◽  
...  
Keyword(s):  
Heart Rate ◽  
Gas Exchange ◽  
Oxygen Uptake ◽  
Metabolic Responses ◽  
Physiological Data ◽  
Respiratory Gas Exchange ◽  
Gum Chewing ◽  
Arterial Blood ◽  
Before And After ◽  
Exercise Induced

Favier, Roland, Esperanza Caceres, Laurent Guillon, Brigitte Sempore, Michel Sauvain, Harry Koubi, and Hilde Spielvogel. Coca chewing for exercise: hormonal and metabolic responses of nonhabitual chewers. J. Appl. Physiol. 81(5): 1901–1907, 1996.—To determine the effects of acute coca use on the hormonal and metabolic responses to exercise, 12 healthy nonhabitual coca users were submitted twice to steady-state exercise (∼75% maximal O2 uptake). On one occasion, they were asked to chew 15 g of coca leaves 1 h before exercise, whereas on the other occasion, exercise was performed after 1 h of chewing a sugar-free chewing gum. Plasma epinephrine, norepinephrine, insulin, glucagon, and metabolites (glucose, lactate, glycerol, and free fatty acids) were determined at rest before and after coca chewing and during the 5th, 15th, 30th, and 60th min of exercise. Simultaneously to these determinations, cardiorespiratory variables (heart rate, mean arterial blood pressure, oxygen uptake, and respiratory gas exchange ratio) were also measured. At rest, coca chewing had no effect on plasma hormonal and metabolic levels except for a significantly reduced insulin concentration. During exercise, the oxygen uptake, heart rate, and respiratory gas exchange ratio were significantly increased in the coca-chewing trial compared with the control (gum-chewing) test. The exercise-induced drop in plasma glucose and insulin was prevented by prior coca chewing. These results contrast with previous data obtained in chronic coca users who display during prolonged submaximal exercise an exaggerated plasma sympathetic response, an enhanced availability and utilization of fat (R. Favier, E. Caceres, H. Koubi, B. Sempore, M. Sauvain, and H. Spielvogel. J. Appl. Physiol. 80: 650–655, 1996). We conclude that, whereas coca chewing might affect glucose homeostasis during exercise, none of the physiological data provided by this study would suggest that acute coca chewing in nonhabitual users could enhance tolerance to exercise.

Some Aspects of Gas Exchange in Tuna

1972 ◽  
Vol 56 (3) ◽  
pp. 809-823
Author(s):  
E. D. STEVENS
Keyword(s):  
Hydrostatic Pressure ◽  
Gas Exchange ◽  
Oxygen Uptake ◽  
Average Rate ◽  
Oxygen Removal ◽  
Skipjack Tuna ◽  
Partial Pressure Of Oxygen ◽  
Free Swimming ◽  
Flow Rates ◽  
Theoretical Predictions

1. Some aspects of gas exchange in restrained skipjack tuna were analysed. 2. The average rate at which water flowed over the gills was 2.81/min. kg. 3. The concentration of oxygen in water entering and leaving the gills was measured and used to calculate oxygen uptake (692 mg/h.kg) and utilization (0.71). 4. The drop in hydrostatic pressure as water flowed over the gills was 1.9 cm water and agrees favourably with theoretical predictions. 5. The partial pressure of oxygen was measured in blood afferent and efferent to the gills and used to calculate effectiveness of oxygen removal from the water (90%) and the transfer factor for oxygen (0.12 ml/min.kg.mmHg). 6. The average utilization measured in free-swimming tuna was 0.56. 7. The extraordinary ability of tuna to efficiently extract oxygen from the water at high gill water flow rates is discussed.

Ventilation and gas exchange in lizards during treadmill exercise.

1997 ◽  
Vol 200 (20) ◽  
pp. 2629-2639
Author(s):  
T Wang ◽  
D R Carrier ◽  
J W Hicks
Keyword(s):  
Exchange Rate ◽  
Gas Exchange ◽  
Oxygen Uptake ◽  
Minute Ventilation ◽  
Oxygen Demand ◽  
Lung Ventilation ◽  
Iguana Iguana ◽  
Maximal Aerobic Speed ◽  
Gas Exchange Rate ◽  
Treadmill Locomotion

The extent to which lizards ventilate their lungs during locomotion is controversial. Direct measurements of airflow across the nostrils suggest a progressive reduction in tidal volume and minute ventilation with increased running speed, while other studies have demonstrated that arterial PO2 remains constant during exercise. To resolve these conflicting findings, we measured minute ventilation and gas exchange rate in five specimens of Varanus exanthematicus and five specimens of Iguana iguana during treadmill locomotion at speeds between 0.14 and 1.11ms-1 at 35 degrees C. These speeds are much lower than maximal running speeds, but are greater than the maximal aerobic speed. In both species, the ventilatory pattern during locomotion was highly irregular, indicating an interference between locomotion and lung ventilation. In Varanus exanthematicus, treadmill locomotion elicited a six- to eightfold increase in minute ventilation from a pre-exercise level of 102mlkg-1min-1, whereas the rate of oxygen uptake increased approximately threefold (from 3.9 to 12.6mlkg-1min-1). After exercise, both minute ventilation and gas exchange rate decreased immediately. Because minute ventilation increased more than did oxygen consumption, an increase in lung PO2 during exercise is predicted and, thus, Varanus exanthematicus appears effectively to ventilate its lungs to match the increased metabolic rate during locomotion at moderate speed. In Iguana iguana, both minute ventilation and gas exchange rate increased above resting values during locomotion at 0.28ms-1, but both decreased with further increases in locomotor speed. Furthermore, following exercise, both minute ventilation and oxygen uptake rate increased significantly. Iguana iguana, therefore, appears to be unable to match the increased oxygen demand with adequate ventilation at moderate and higher speeds.

Seed Germination in Ruzizi Grass (Brachaaria ruziziensis Germain & Evrard)

1976 ◽  
Vol 24 (4) ◽  
pp. 437 ◽  
Author(s):  
C Renard ◽  
P Capelle
Keyword(s):  
Hydrogen Peroxide ◽  
Seed Germination ◽  
Gas Exchange ◽  
Oxygen Uptake ◽  
Oxidizing Agents ◽  
Brachiaria Ruziziensis

Sowing is the most common way of establishing Brachiaria ruziziensis in pastures, but seed germi- nation is poor as a result of dormancy. The mechanism of dormancy is clearly located in the hull, for removing the hull or cutting at the base of the spikelet stimulates germination. No leachable inhibitor seems to be the cause of dormancy. However, the action of oxidizing agents such as hydrogen peroxide and the measurement of oxygen uptake by full or empty spikelets suggest that a restriction of gas exchange by the hull is responsible.

scholarly journals Thermoanalytische Untersuchungen zur Rückoxidation von Ba2YCu3O6+x

1988 ◽  
Vol 43 (11) ◽  
pp. 965-970 ◽  
Author(s):  
Chr. L. Teske ◽  
Hk. Müller-Buschbaum
Keyword(s):  
Activation Energy ◽  
Oxygen Uptake ◽  
Ceramic Material ◽  
Maximum Rate ◽  
Reaction Enthalpy ◽  
Super Conducting ◽  
Dta And Tg ◽  
Superconducting Ceramic

Abstract The reoxidation reaction of Ba2YCu3O6+ x forming the superconducting ceramic material Ba2YCu3O6 93 is studied by thermoanalytical methods (DTA and TG). The exothermal oxygen uptake in pure O2-atmosphere is at a maximum rate in the range of 230-330 °C (≈ 150min). The reoxidation temperature can be lowered by treatment of Ba2YCu3O6 0 in Ar : H2 = 1: 1 atmosphere but the uptake of greater amounts of hydrogen prevents the material from becoming super-conducting again at low reoxidation temperatures. The process has an activation energy Ea = 70.9 ± 2kJ Mol and a reaction enthalpy ΔH = - 86.7kJ/Mol Ba2YCu3O6.0 (normalized to a 1/2 O2 basis) which is estimated from DTA-data.

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